This circuit with TTL compatible output was found in a 1968 US documentation. The circuit is powered by 5 V and the frequency can be changed by changing the crystal.
This circuit transmits the sound signals from a television or amplifier to an FM receiver at up to...
This is one of the first games that came out in the 70s. This one is from a Radio Electronics...
We found this circuit in an old American documentation. The operational amplifier is not common...